There is presently a preference in certain industries for degradable and bioabsorbable polymers over traditional polymers such as polystyrene and poly(ethylene terephthalate) (PET). Traditional biodegradable polymers incorporate a degradable linkage into the backbone that can be cleaved by hydrolytic, enzymatic and oxidative processes. Examples of traditional biodegradable polymers include polyamides, polyanhydrides, polycarbonates, polyesters, polyesteramides, and polyurethanes. Aliphatic polyesters, specifically poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA) and poly(ε-caprolactone) (PCL), have found use in biomedical soft material applications, such as drug and gene delivery, sutures, stents, dental implants and as tissue engineering scaffolding. Unfortunately, these polyesters may only be functionalized on the chain ends, and the conditions for preparing polyesters are not suitable to many functional groups. Presently, there is a need in the art to produce polyesters with properties that are tunable through pendant functionalization.
Hyperbranched polymers are another class of polymers where the ability to tune properties through functionalization is desired. Hyperbranched polymers are in the class of chemically similar polymers having different molecular architecture can exhibit various interesting properties that are different than the polymers of conventional architectures (like linear and branched, cross-linked polymers). Most importantly and distinctly, shear thinning behavior and lower viscosity of these polymers give processing advantages compared to the linear counterparts. This new class of architecture mainly consists of dendrimers and hyperbranched polymers. In contrast to dendrimers, which have uniform distribution of branches in three dimensions, hyperbranched polymers are characterized by random and non-uniform branching. It has been suggested in the reported literatures that dendrimers can successfully be employed in certain applications to achieve improved properties, especially processing properties. Due to lack of entanglements of the chains, the viscosity of these polymers is lower than that of linear polymers. Dendrimers are monodisperse (typically have polydispersity 1.02 or less) and synthesized with controlled step-growth reactions with tedious protection-deprotection strategies and purification. In contrast, hyperbranched polymers may be made from one-step, one-pot reactions and are polydisperse. This facilitates the synthesis of a large amount of polymers with higher yield at comparatively lower cost. Due to its imperfect branching and higher polydispersity, the properties of hyperbranched polymers lie between those of dendrimers and linear polymers. This wide window of properties between these of the two extreme architectures makes hyperbranched polymers a potential competitor superior to dendrimers in certain applications. Hyperbranched polymers, and particularly hyperbranched polymers prepared with acrylates, may be used in a variety of applications, for example, ingredients in paints, coatings, textiles, adhesives, superabsorbent materials, contact lenses, display devices, polyelectrolytes & hydrogels. Hyperbranched polymers have reactive end groups that can be modified and used advantageously in coating and additive applications. However, the ability to further tune the properties of hyperbranched polymers through the inclusion of additional functional groups is desired.